Thermoplastic planks and methods for making the same

ABSTRACT

A thermoplastic laminate plank is described wherein the thermoplastic laminate plank comprises a core, a print layer, and optionally an overlay. The core comprises at least one thermoplastic material and has a top surface and bottom surface wherein a print layer is affixed to the top surface of the core and an overlay layer is affixed to the top surface of the print layer. Optionally, an underlay layer can be located and affixed between the bottom surface of the print layer and the top surface of the core. In addition, a method of making the thermoplastic laminate plank is further described which involves extruding at least one thermoplastic material into the shape of the core and affixing a laminate on the core, wherein the laminate comprises an overlay affixed to the top surface of the print layer and optionally an underlay layer affixed to the bottom surface of the print layer.

This application is a continuation of U.S. patent application Ser. No.09/630,121 filed Aug. 1, 2000, which in turn is a continuation-in-partof prior U.S. patent application Ser. No. 09/460,928 filed Dec. 14,1999, now U.S. Pat. No. 6,617,009 B1 and is incorporated in its entiretyby reference herein.

BACKGROUND OF THE INVENTION

Commercially available laminate flooring (using high or medium densityfiberboard or particle board as the core layer) has gained overwhelmingsuccess in the flooring market. The growth rate of the laminate flooringhas remained in the double digits since the product was introduced inthe United States market. The success of this product is credited tocertain properties such as stain resistance, wear resistance, fireresistance, good cleanability, and the ability to use just about anytype of printed design. In addition, the overall emission of organiccompound vapor is low and the laminate flooring is considered colorstable and environmentally friendly over other competing flooringproducts.

The biggest concern with commercially available laminate flooring is themoisture resistance of the finished product and the sensitivity of theraw materials (high or medium density fiberboard, paper, and particleboard) to moisture during the manufacturing process. In some instances,the moisture can lead to some serious quality control issues andapplication restraints. For instance, and just to name a few, the highermoisture content in the product, such as in the particle board orfiberboard, can cause blistering and adhesion failure of the melaminesurface to the core. Also, higher moisture contents can lead todimensional instability of the finished product, which then results inthe cupping or doming of the product, which is extremely undesirable,especially when installers are laying down the flooring. Also, excessivemoisture contents can create edge peaking due to the swelling of theproduct and such edge peaking can result in edge chip-off or prematurewear-out or can soil more quickly. The susceptibility to moisturecontent also leads to some installers not wishing to place such laminateflooring in areas which are subject to having water on the surface ofthe floor, such as in the kitchen and bathroom areas.

The suppliers of such laminate flooring have appreciated the problemsassociated with their products and have attempted to overcome theseproblems by developing laminate flooring having better moistureresistance by using melamine, phenolic, or isocyanate binders topartially replace urea resins present in the laminate flooring. Whilethis improvement has made the product more moisture resistant, thecurrent commercially available laminate floorings are still prone tomoisture damage. For instance, the thickness swelling of laminateflooring can increase by 10% and water absorbency can exceed more than15% according to the 24 hours water absorption test. Another attemptedsolution at the moisture resistance weaknesses of current laminateflooring has led some manufactures to apply a water-repellant materialon the upper edges of the tongue and groove areas which further serve toresist any moisture penetration through joints. Still another attemptedsolution involves applying silicone caulk to seal the edges and voids ofthe laminate perimeter where the laminate flooring meets the wall.However, if very stringent installation instructions are not followed,the laminate flooring will still be subjected to moisture damage.

Accordingly, there is a need to develop a laminate flooring system whichovercomes the above weaknesses and disadvantages of current commerciallyavailable laminate flooring.

SUMMARY OF THE INVENTION

A feature of the present invention is to provide a laminate plank whichcan be used in a surface covering system which provides improvedmoisture resistance and is not susceptible to damage caused by moisture.

Another feature of the present invention is to provide a laminate plankand surface covering system which is economically feasible and permitseasy installation and flexibility.

A further feature of the present invention is to provide a flooringsystem that improves foot comfort and other ergonomic benefits.

An additional feature of the present invention is to provide a surfacecovering system having improved sound deadening and other reduced soundtransmission benefits.

Still another feature of the present invention is to provide a surfacecovering system which has significant improvements with respect to easeof installation and includes a fool-proof installation design andtechnique.

Another feature of the present invention is to provide a surfacecovering system which avoids the use of a wet adhesive applicationmethod.

Another feature of the present invention is to provide a flooring systemthat has great flexibility so as to make various shapes, sizes, andbevel edges.

Another feature of the present invention is to provide a flooring systemthat can alleviate the requirement of installing the plank in a givenorientation.

Also, a feature of the present invention is provide a surface coveringsystem which has the ability to tolerate some imperfections in thesub-floor or substrate and thus avoid telegraphing the imperfections onthe surface covering itself.

A further feature of the present invention is to provide a surfacecovering system which has improved damaged resistance properties, suchas improved impact strength and the like.

Additional features and advantages of the present invention will be setforth in the description which follows, and in part will be apparentfrom the description, or may be learned by practice of the presentinvention. The features and other advantages of the present inventionwill be realized and attained by means of the elements and combinationsparticularly pointed out in the written description and appended claims.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described herein, thepresent invention relates to a thermoplastic laminate plank, wherein thelaminate plank has a core comprising at least one thermoplasticmaterial, wherein the core has a top surface and a bottom surface.Optionally affixed to the top surface of the core can be a print layer,wherein the print layer has a top surface and a bottom surface. Also, anoverlay layer can be affixed directly to the top surface of the core,or, if a print layer is provided, affixed to the top surface of theprint layer. The plank can optionally contain an underlay layer locatedand affixed between the bottom surface of the print layer and the topsurface of the core.

The present invention further relates to a method of making athermoplastic laminate plank and involves the step of processing (e.g.,extruding) at least one thermoplastic material into the shape of a coreand optionally affixing a laminate on the core, wherein the laminate cancomprise a print layer, an overlay layer affixed to the top surface ofthe print layer, and optionally an underlay layer affixed to the bottomsurface of the print layer.

Also, the present invention relates to a method of making athermoplastic plank by printing a design directly on the top surface ofthe plank using any number of printing techniques, such as gravureprinting, transfer printing, digital printing, Flexo printing, screenprinting, and the like. The method can also include applying aprotective coating on top of the printed design, such as a polyurethanetype coating with or without wear resistant particles in the coating.The top surface of the plank can also be treated or formed to have atextured finish such as a roughed, grooved, cross-hatched, striated,pitted, cracked, or wood grain or streak texture. In addition,decorative foils or printed overlays can be affixed to the top surfaceof the plank and then covered by a protective coating(s).

A further embodiment of the present invention relates to making athermoplastic plank for flooring by co-extrusion techniques, whichinvolves extruding at least one thermoplastic material into the shape ofthe core and also extruding a layer containing at least onethermoplastic material with one or more pigmented compounds on top ofthe extruded core, wherein the layer simulates a design, such as woodgrain or marble.

The present invention also relates to thermoplastic planks having theabove-described characteristics.

It is to be understood that both the forgoing general description andthe following detailed description are exemplary and explanatory onlyand are intended to provide further explanation of the presentinvention, as claimed.

The accompanying drawings, which are incorporated in and constitute apart of this application, illustrate several embodiments of the presentinvention and together with the description serve to explain theprinciples of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing an end view of one embodiment of athermoplastic laminate plank of the present invention.

FIG. 2 is a schematic diagram showing a side view of a spline designwhich can be used to connect together the planks of the presentinvention.

FIG. 3 is a schematic diagram of a sectional view showing anotherembodiment of a thermoplastic laminate plank of the present invention.

FIG. 4 is a schematic diagram showing a groove design for a connectoruseful in connecting the planks of the present invention.

FIGS. 5 and 6 are schematic diagrams showing end views of additionalembodiments of the thermoplastic laminate plank of the presentinvention.

FIG. 7 is a schematic diagram showing an end view of an additionalembodiment of the thermoplastic plank of the present invention.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

In general, the present invention relates to a thermoplastic laminateplank which contains a core comprising at least one thermoplasticmaterial. This core has a top surface, a bottom surface, and at leastfour sides or edges. Located or affixed on the top surface of the corecan be a print layer having a top surface and a bottom surface.Optionally located or affixed onto the top surface of the print layer isan overlay layer having a top surface and a bottom surface. Thethermoplastic laminate plank of the present invention can optionallyfurther include an underlay layer which is located and affixed betweenthe bottom surface of the print layer and the top surface of the core.

In more detail, the core in the thermoplastic laminate plank is made ofat least one thermoplastic material. Generally, any thermoplasticmaterial, combinations thereof, alloys thereof, or mixtures of two ormore thermoplastics can be used to form the core. Generally, suchthermoplastic materials include, but are not limited to, vinylcontaining thermoplastics such as polyvinyl chloride, polyvinyl acetate,polyvinyl alcohol, and other vinyl and vinylidene resins and copolymersthereof; polyethylenes such as low density polyethylenes and highdensity polyethylenes and copolymers thereof; styrenes such as ABS, SAN,and polystyrenes and copolymers thereof, polypropylene and copolymersthereof, saturated and unsaturated polyesters; acrylics; polyamides suchas nylon containing types; engineering plastics such as acetyl,polycarbonate, polyimide, polysufone, and polyphenylene oxide andsulfide resins and the like. One or more conductive polymers can be usedto form the plank, which has applications in conductive flooring and thelike. The thermoplastic polymers set forth in Kirk Othmer (3^(rd)Edition, 1981) at pp. 328 to 848 of Vol. 18 and pp. 385–498 of Vol. 16,(incorporated in their entireties by reference herein) can also be usedas long as the resulting plank has sufficient strength for its intendedpurpose.

Preferably, the thermoplastic material is a rigid polyvinyl chloride butsemi-rigid or flexible polyvinyl chloride may also be used. Theflexibility of the thermoplastic material can be imparted by using atleast one liquid or solid plasticizer which is preferably present in anamount of less than about 20 phr, and more preferably, less than 1 phr.A typical rigid PVC compound used in the present invention to form thecore can also include, but is not limited to, pigments, impactmodifiers, stabilizers, processing aids, lubricants, fillers, woodflours, other conventional additives, and the like.

The thermoplastic polymer compound to be processed can be in powder,liquid, cubed, pelletized and/or any other extrudable form. Also, thethermoplastic polymer can be virgin, recycled, or a mixture of both.Furthermore, the thermoplastic material can be incorporated with ablowing agent(s) or a mechanically injected gas during the extrusionprocess to make a cellular foam structure core.

The thermoplastic material used to form the core, which is preferablypolyvinyl chloride, is preferably a suspension grade or masspolymerization grade homopolymer resin having a preferred molecularweight as reflected by an inherent viscosity of from about 0.88 to about1.0 inherent viscosity. In general, a higher molecular weight polymer ispreferred from the standpoint of processing stability and preferably themolecular weight distribution and particle size distribution are narrowin order to provide a good balance between processability andproperties. Also, high porosity and uniform porosity of the resinparticles are preferred to optimize compounding and processing aspects,including the fast and uniform absorption of any stabilizer that ispresent as well as other ingredients during compounding.

Preferably, the thermoplastic material used to form the core is a rigidPVC powder compound that has good impact strength, ease of processing,high extrusion rate, good surface properties, excellent dimensionalstability, and indentation resistance.

The preferred thermoplastic polymer used to form the plank is apolyvinyl chloride from The Geon Company designated X150-206-050-02,which has the following formula:

FORMULATION PARTS BY WEIGHT Extrusion Grade PVC (0.88–0.96 IV) 100 TinMercaptide Stabilizer 2–4 PVC Acrylic Processing Aid 1–3 Filler 10–30Impact Modifier (Acrylic)  3–10 Lubricant Package 2–5 Pigment 1–5

The polyvinyl chloride preferably has the following properties:

GEON COMPOUND ASTM METHOD 87150 Type Powder Cell Classification D178413344-C Specific Gravity 0.2 D792 1.45 Hardness-Durometer Shore D 3D2240 82 Tensile Properties - Strength PSI D638 6000 TensileProperties - Modulus PSI D638 390000 Flexural Properties - Strength PSID790 11000 Flexural Properties - Modulus PSI D790 370000 Heat DeflectionTemperature F. D648 160 Unannealed @ 1.82 MPa (264 PSI) Coefficient ofLinear Expansion D696 3.4 × 10⁻⁵ in./in. F Notched IZOD Ft.lb./in. ofnotch @ D256 3 23 C. (73 F.) Impact Properties - Drop Impact D4226 1.0in.lb/mil @ 375 F. melt T. ¼″ Dart H.250 Method A 1.0 ¼″ Dart H.250Method B 1.0 ⅛″ Dart H.125 Method A 1.0 ⅛″ Dart H.1250 Method B

Generally, this compound will have a melt temperature of from about 360to about 390° F. Preferably, a stabilizer is also present in thethermoplastic formulation that forms the core. A preferred stabilizer isa butyl tin mercaptide stabilizer. In addition, an impact modifier isalso preferably present and preferred impact modifiers are acrylic-basedfrom Rohm and Haas, an EVA-based impact modifier known as Elvaloy™ fromDuPont; and others such as chlorinated polyethene and acrylonitrilebutadiene styrene, and the like.

In addition, the thermoplastic formulation preferably contains at leastone processing aid which is preferably an acrylic based low molecularweight resin such as Acryloid K-125 or K-175 from Rohm and Haas. Also,at least one lubricant is preferably present and more preferably aninternal lubricant and an external lubricant. Preferred internallubricants, which act internally to alter the cohesive forces amongstthe polymer chains that results in lower melt viscosity without reducingthe strength properties of the resin, are metallic stearates such ascalcium and zinc salts of stearic acid. External lubricants, which actexternally to prevent resins from sticking to hot metal processingmachinery by reducing friction between the surfaces, are preferablylow-melting paraffins. Fillers are preferably added to the thermoplasticformulation to reduce product cost and to improve impact properties.While any filler can be used as long as it is compatible with thethermoplastic resin, typical fillers include, but are not limited to,calcium carbonate.

The thermoplastic core can be made of a thermoplastic resin and asurface roughening agent, if a rough top surface of the core is desired.Surface roughening agents can impart a non-slip surface to the core orprovide a rough surface that is more receptive to some adhesives than asmooth surface would be. Exemplary surface roughening agents includepowdered materials having particle sizes of about 1000 microns or less,and may comprise silicon glass particles, pigments, TEFLON® powders,flour, cornstarch, siliconized glass powders, and micronized cellulosicpowders. Inert powders are preferred, including TEFLON® powders, TEFZEL®powders, KYNAR™ powders, polypropylene micropowders, and TULLANOX™micropowders. The surface roughening agents can be mixed into thethermoplastic melt before the planks are extruded or applied to thesurface of the extruded plank while hot, so as to become affixed to thesurface.

Preferably, the thermoplastic core is rigid in nature and has thefollowing range of preferred properties: impact resistance, static loadresistance, indentation resistance, moisture insensitivity, pre-profiledconfiguration, and the like.

While the core can be made in a number of ways, preferably the core isformed by an extrusion process wherein the thermoplastic material alongwith any other optional ingredients are blended together and are thenfed into an extruder by a feeder wherein the extruder with theapplication of heat and auger action melts the thermoplastic material tothe extent that it is eventually fed through a die, wherein the die isin the shape of the core.

In more detail, the extrusion process permits a) an economicallyfeasible design by designing a profile with cavities inside thestructure and b) a highly versatile method of achieving the complicatedprofile design of the preferred plank without additional machiningafterwards for the tongue and groove, for instance. While any extrudercan be used which can extrude the desired design of the plank forthermoplastic materials, preferably the extruder is one from AmericanMaplan corporation such as model TS-88 which has the ability to processrigid PVC profiles with a maximum output capacity of about 900 lb/hr,based upon a compound bulk density of 37 lb/ft³. The TS-88 is a twinscrew extruder which has a barrel heating section and a cooling sectionas well as a vacuum system. In the extruder, there can be 12 temperaturezones with 6 for cooling and a temperature control system.

The dimensions of the core can practically be any shape or size as longas such material can be extruded as one piece or multiple pieces. Forinstance, the core preferably has a thickness of from about 3 mm toabout 50 mm, a width of from about 2 cm to about 60 cm, and a length offrom about 30 cm to about 215 cm. The core can preferably have a squareor rectangular shape. An exemplary core has a width of up to seveninches (18 cm) or more and a length of about 72 inches (183 cm) or more.An exemplary rectangular core has a width of about five inches (13 cm)and a length of about 72 inches (183 cm). Also, the top surface of thecore can optionally have a textured surface on the top surface as partof the core which is extruded through the die. The top surface of theplank can also be treated or formed to have a textured finish such as aroughed, grooved, cross-hatched, striated, pitted, cracked, or woodgrain texture. A mechanical embossing roller can be located behind thecooling calibrator and after the extrusion die to achieve surfacetexturing of the extruded core. Any variety of textures can be createdby this method on the core such as wood grains and the like.

Also, as an option, the core can be 100% solid or can have one or morecavities or cells which are located between the upper and lower surfacesof the core. While the cavities are optional, the cavities are preferredsince they reduce the amount of thermoplastic material used and create alighter weight product. The cavities or cells which can be part of theextruded core preferably have cavities having dimensions of from about 3mm to about 16 mm in height, by about 6 mm by about 20 mm in width, andcan be separated by solid thermoplastic material walls havingthicknesses of from about 1.0 mm to about 3.02 mm. The optimal dimensionof cavities is dependent upon the requirement of the product towithstand the potential impact force of falling objects. The cavitieswhich are preferably present can be of any cross-sectional shape such asrounded, oval, triangular, or rectangular. These cavities or cellspreferably exist across the entire distance of the core as shown inFIGS. 1, 5, and 6. Preferably, each cavity extends longitudinally alongthe entire length of the plank, although the cavities can instead extendlatitudinally along the entire width of the plank. Preferably, thecavities extend in the direction of extrusion of the thermoplastic plankmaterial.

Another advantage is that wires, cables, fiber optics, and/or piping canbe run through the cavities which makes installation of wiring andpiping quite easy without the necessity of putting holes through walls,or running wires underneath the floor or in the ceiling. Further, ifnecessary, holes can be drilled through the thermoplastic materialseparating one cavity from another in order to have the wire or pipinggo in a perpendicular direction when necessary. Alternatively, forcertain thermoplastic core pieces, the cavities can be run in aperpendicular direction from the remaining pieces in order toaccommodate the direction that wiring or piping may take when beingplaced in a room.

According to some embodiments of the invention, electric wires, phonelines, cable television lines, speaker wires, heating elements, hot orcold air conduits, or the like can be integrally extruded within thethermoplastic material of each plank and suitable terminals orconnectors, such as pin and hole connectors, can be formed on the endsof the planks and connected to each wire, conduit, or the like. In thismanner, a series of planks can be pieced together and carry, forexample, a speaker signal from one end of a floor to another end of thefloor. Heated or cooled floors can be manufactured having connectingconduits through which adjacent planks can carry hot or cold air.

The cores which form the plank are preferably all made from the same diedesign and thus they are uniform in appearance. Also, the cavities whichare preferably present in the core align with the cavities in respectivecore pieces. Dowels or other equivalent material can be inserted intothe cavities at the short end of the plank in order to join an adjacentplank to create a tight seal at each seam. The ends of the planks canhave formed therein grooves for receiving a toothed spline or otherconnecting member so that the ends of adjacent planks can be joinedtogether in the same manner, or in a similar manner, as the side edgesof the planks are joined. The end grooves can be cut or otherwise formedin the extruded planks after extrusion. One end of each plank can beprovided with one or more alignment or centering pins while the oppositeend of each plank can be provided with one or more recesses, holes, oropenings for receiving an alignment pin from an adjacent plank. Thesetypes of coupling systems, though optional, will further ensure a verysecure tight fitting floating floor or other surface covering.

Though not necessary, the ends of the plank as well as the tongue and/orgroove can have a bonding agent applied to these locations in order toseal or bond the planks together. Surprisingly, the inventors havediscovered that sealant compositions such as tetrahydrofuran have theability to actually work as a bonding agent to join the planks together.In one of the examples that follows, the results show that by usingtetrahydrofuran or compositions like tetrahydrofuran, the joints of theplanks which have been attached with the use of this composition leadsto the formation of a bond between the planks and increases the overallbond strength of two adjoining boards significantly. The use of thisbonding agent can be used not only with the planks described above butwith all thermoplastic planks, provided the bonding agent is capable ofsolvating or dissolving the particular plastics to form a chemicaland/or mechanical bond. One advantage of using a bonding agent liketetrahydrofuran is that it is effective, it is simple to use, and leavesno residue on the surface after evaporation. Thus, no adhesive marks areleft on the surface of the planks. In addition, applying such bondingagents like tetrahydrofuran is quite easy since it can be applied bybrush or spray or applicator tip using gravity or other force such assqueezing an applicator bottle, and any excess is easily removed unlikethe application of some adhesives for tiles and the like. Other examplesof other suitable bonding agents which have this ability to bond thethermoplastic planks include, but are not limited to, methylene chlorideand ketones and the like. Examples of ketones include, but are notlimited to, methyl ethyl ketone, methyl amyl ketone, dipropyl ketone,methyl isobutyl ketone, n-methyl pyrrolidone, dimethyl formamide,cyclohexanone, nitrobenzene, and the like.

Another optional aspect of the core is the presence of a groove and/or atongue design on preferably two or more sides or edges of the corewherein the sides or edges are opposite to each other. While the coredesign can have a tongue design on one edge and a groove design on theopposite edge, it is preferred that both edges which are opposite toeach other have a groove design. This tongue and/or groove design on thecore can be formed as part of the extruded core. The tongue or groovecan have a variety of dimensions but preferably the groove which ispresent on two, opposite edges has internal depth dimension of fromabout 5 mm to about 12 mm and a height of from about 3 mm to about 5 mm.The bottom width of the side having the groove is slightly shorter thanthe upper width of the same side to ensure no gap exists between planksafter butting together. In other words, the bottom lip of the groove isslightly narrower than the top lip, ensuring the top lip oflaterally-adjoining planks will meet before the bottom lips. Thisensures no visible surface gap. In addition, it is preferred that thegroove have teeth located on the upper surface and lower surface of thegroove to receive an interlocking tongue, wherein the tongue is aseparate component which will be described later. The teeth which canpreferably be present as part of the extruded groove forming part of theextruded core are preferably from about 0.2 mm to about 1.2 mm in sizefor each tooth and having an angle of from about 30 to 45 degrees with abackward bite enabling easier insertion than removal of the tongueportion. A preferred design is set forth in FIGS. 3 and 4.

Also, as an option, any edge, and preferably the edges which preferablyhave the tongue and/or groove, are preferably tapered or beveled so thatwhen two cores are brought together for attachment, a valley or V-shapedrecess is formed. Preferably, the tapered or beveled edges are at anangle of from about 15° to about 55°, and more preferably at about a 17°angle. Also, the length of the beveled or tapered edge is about 2.0 mmto about 7.0 mm on each core piece. A preferred design is set forth inFIG. 3.

As another option, the core can have located on its bottom surface anynumber of bottom feet which are preferably pieces of rubber orthermoplastic material which are attached to the bottom surface of thecore. Preferably, the bottom feet are thermoplastic material and morepreferably are soft thermoplastic material which are post-extruded ontothe bottom surface of the plank. While the bottom feet can have anydimensions, preferably the bottom feet have an outer dimension of fromabout 1.0 mm to about 5.0 mm. The bottom feet provide numerous functionssuch as increasing the soft, cushion feeling of the plank to improvefoot comfort level and also reduces the problems associated withsub-floor or substrate imperfections. The bottom feet can also assist incontrolling sound transmissions, and thus have sound deadeningproperties. Also, the bottom feet ensure that migration from any mold,mildew, and/or stain which may be part of the sub-floor or substrate canbe minimized if not eliminated by the bottom feet.

As an additional option, the product with bottom feet can be installedup side down to make a slip resistance floor for such applications asescalators or stairways. The bottom feet are located on the bottomsurface of the core and preferably appear as a series of raised parallelrods running longitudinally along the bottom of the plank. These may beformed by post-extruding soft polymeric rods into depressed groovespresent in the extruded core plank bottom. These raised feet extendoutward from the bottom of the plank and act to support the core abovethe subfloor or substrate. Typically, the post extruded material extendsbeyond the bottom surface from the core by about 10 mils (0.25 mm) toabout 75 mils (2.0 mm), and more preferably from about 25 mils (0.65 mm)to about 50 mils (1.3 mm). FIGS. 1, 3, 5, and 6 further show embodimentsof how the post extruded rods of thermoplastic material can serve as asupport mechanism.

With respect to the laminate on top of the core, a print layer isaffixed to the top surface of the core, wherein the print layer has atop surface and a bottom surface. The print layer preferably is anaminoplast resin impregnated printed paper. Preferably, the print layerhas a printed design. The printed design can be any design which iscapable of being printed onto the print layer. The print layer is alsoknown as a decor print layer. Generally, the print layer can be preparedby rotogravure printing techniques or other printing means such asdigital printing. Once the paper has the design printed on it, the paperis then impregnated with an aminoplast resin or mixtures thereof.Preferably the aminoplast resin is a blend of an urea formaldehyde and amelamine formaldehyde.

The print paper, also known as the Deco paper, preferably should havethe ability to have liquids penetrate the paper such as a melamineliquid penetrating in about 3 to 4 seconds and also maintain a wetstrength and even fiber orientation to provide good reinforcement in alldirections. The print paper used doesn't need to impregnate with theresin (this is optional), but instead relies on slight resin migrationfrom the adjoining layers during the lamination process (applying heatand/or pressure to laminate all layers to one). Preferably, the resinused for the impregnation is a mixture of urea formaldehyde and melamineformaldehyde resins. Urea formaldehyde can contribute to the cloudinessof the film that is formed and thus is not preferred for dark colors andthe melamine resin imparts transparency, high hardness, scratchresistance, chemical resistance, and good formation, but may have highshrinkage values. Combining urea resins with melamine resins in amixture or using a double impregnation (i.e., applying one resin afteranother sequentially) provides a positive interaction in controllingshrinkage and reducing cloudiness. Preferably, the type of paper used is75 g/m² weight and having a thickness of 0.16 mm. The saturation of thecoating preferably is about 64 g/m².

Located optionally on the top surface of the print layer is an overlay.The overlay which can also be known as the wear layer is an overlaypaper, which upon being affixed onto the print layer, is clear inappearance. The overlay paper is preferably a high abrasive overlaywhich preferably has aluminum oxide embedded in the surface of thepaper. In addition, the paper is impregnated with an aminoplast resinjust as with the print layer. Various commercial grades of high abrasiveoverlays are preferably used such as those from Mead Specialty Paperwith the product numbers TMO 361, 461 (70 gram/m² premium overlay fromMead), and 561 wherein these products have a range of Taber values of4000 to 15000. The type of paper preferably used has a weight of about46 g/m² and a thickness of about 0.13 mm.

With respect to the print layer and the overlay, the amount ofaminoplast resin is preferably from about 60 to about 140 g/m² and morepreferably from about 100 to about 120 g/m².

As an option, an underlay can be located and affixed between the bottomsurface of the print layer and the top surface of the core. Preferablythe underlay is present and is paper impregnated with an aminoplastresin as described above with respect to the print layer and overlay.Preferably, the underlay is Kraft paper impregnated with aminoplastresins or phenolics and more preferably phenolic formaldehyde resin ormelamine formaldehyde resin which is present in an amount of from about60 g/m² to about 145 g/m² and more preferably from about 100 g/m² toabout 120 g/m² paper. The type of paper used is preferably about 145g/m² and having a thickness of about 0.25 mm. The underlay is especiallypreferred when extra impact strength resistance is required.

Preferably, the thermoplastic laminate plank can be prepared byextruding the core as described above and forming a laminate comprisingthe overlay affixed to the top surface of the print layer and optionallythe underlay layer which is affixed to the bottom surface of the printlayer. This laminate can be prepared, for instance, by any processcustomarily used to manufacture laminate films such as a continuousdouble belt press. In general, the underlay, if used, the print layerand the overlay can be fed into a continuous double belt press thatserves as a laminating calendar. Preferably, the continuous operation isan isobaric system wherein pressures can go as high as 30 bar and theline speed can be up to 20 meters per minute. The pressure zone lengthis about 2–3 meters. In this continuous double belt press system, theisobaric system provides a steady uniform pressure effect on each pointof the treated surface of the laminate. Embossing of the laminate can beaccomplished by embossed release paper or the belt of the double beltpress can be embossed to produce surface textures. In a continuousdouble belt press, the simultaneous heating of the laminate with properdwell time and pressure forms the laminate film which can then be rolledup for subsequent application. Once the laminate is formed it can beapplied onto the core and is preferably affixed by any means, such aswith an adhesive. Preferably the adhesive is a hot melt adhesive such asa hot melt glue like hot melt polyurethane glue.

The hot melt adhesive, such as the hot melt polyurethane adhesive, ispreferably applied to the back surface of the laminate film at apreferred temperature of from about 250° F. to about 300° F., morepreferably from about 250° F. to about 275° F. These temperatures mayvary slightly depending upon the adhesive. The application of the hotmelt adhesive to the laminate can be done by a direct roll coater. Thelaminate with the adhesive on the back surface can then be heated to anadequate temperature to soften the laminate and allow the laminate toform to the profile of the thermoplastic core and thus be affixedpermanently. The typical wrapping machine is designed to hold thelaminate to the contour of the thermoplastic plank as it is being cooledto below about 90 to about 100° F. The thickness of the application ofthe adhesive can have an effect on the impact resistance of the finishedproduct. If the application of the adhesive is too thick, an impact maycause the laminate to become brittle and crack. A thin applicationenables the laminate to flex less during impact and minimize the damage.Application of the adhesive is preferably made at a rate of from about 5to about 15 grams per square foot (g/ft²) and more preferably from about4 to about 8 g/ft². A preferred hot melt adhesive is Ever-Lock®2U145/2U230 modified polyurethane adhesive reactive hot melt fromReinhold Chemicals, Inc.

As described earlier, the various laminate planks of the presentinvention can be connected together by a tongue piece or spline or snapconnector. A separate spline or snap connector is a separate piece andis especially effective when a groove is present on two opposite sidesor edges of the thermoplastic laminate plank. The snap or tongue piececan be inserted into one groove and is long enough to extend outside thegroove and fit into a respective groove of another thermoplasticlaminate plank in order to connect the two pieces together. Preferably,the tongue piece or snap connector is a co-extruded material that ismade of a rigid thermoplastic material such as polyvinyl chloride orpolyvinyl chloride/rubber blends in the central portion and a softthermoplastic material such as soft polyvinyl chloride at the top andbottom surface of the snap connector in order to be flexible wheninserted into the groove so as to securely engage the teeth portions ofthe groove in the preferred embodiment.

The snap connector is designed for ease of installation. To achieve thisobjective is to mechanically interlock two planks together with aconnector without using glue. The connector is to fit into the sidegrooves of two adjoining planks. The purpose of the snap connectorincludes holding the planks together and preventing water pooled on thetop of the joint from penetrating totally through the joint and wettingthe subfloor or surface under the planks.

The snap connector, also known as a spline, has a width large enough toallow the teeth in each adjoining groove to grip the connectorsatisfactorily, but the snap connector must be narrower than thecombined groove depths of the adjoining planks to allow the tops of theplanks to come together (See FIG. 3). Thus, the snap connector should beas wide as possible to provide maximum grab surface, but should benarrow enough to allow the top surfaces of the adjoining planks to meet.The width of the snap connector would preferably range from about 0.007to about 0.013 inches less than the nominal groove depth to allow forprocessing variability. To increase the “bite” of the teeth in thegroove onto the surfaces of the connector, the top and bottom surfacesof the connector may be made of a softer material than the core of theconnector. This material may be comprised of plasticized vinyl, a vinylrubber blend, and the like. One such embodiment contains a hard innercore made of GEON 8700 compound with a total thickness of about 2 mm toabout 3 mm with a top and bottom surface made of GEON 8602 product withthickness of from about 1.3 mm to about 3 mm for each surface.

The snap connector may have a variety of configurations. In one suchconfiguration, the top and bottom surfaces are flat. This will allow theteeth in the top and bottom surfaces of the adjoining grooves to gripthe connector. The thickness of the connector is determined by twofactors. The thicker the connector, the more pressure the groove teethwill apply. However, the connector can not be too thick or the forceneeded by the installer to drive the adjoining planks together will betoo high. In the case of the connector design with flat top and bottomsurfaces, the connector thickness will range preferably to no more thanabout 0.13 mm to about 0.26 mm more than the groove opening of the plankinto which it is being inserted.

Another configuration includes sets of teeth running longitudinally downthe length of the connector. These teeth may appear on both top andbottom surfaces or only on one surface with the other surface beingflat. The teeth preferably will be configured to slant in the opposingdirection to the teeth in the plank groove, thus allowing an“interlocking effect”.

Due to the flexibility of the teeth, a greater extrusion tolerance forthe side groove of the plank can be accommodated. The total thickness ofthe connector may be in excess of 0.9 mm greater than the plank grooveopening and the force required for installation is still acceptable. Theflexibility of the teeth in the connector will depend on the material ofwhich it is made. One such embodiment contains a hard inner core made ofGEON 8700 compound with a total thickness of about 2.8 mm and a top andbottom surface made of GEON 8602 product with thickness of about 0.76 mmfor each surface. The top and bottom surfaces can contain a soft flatlayer of about 0.25 mm from which teeth 0.5 mm long protrudes.

Another configuration allows depressed serrated “valleys” runninglongitudinally in the direction of the connector. These depressedserrations will allow teeth of the grooves in the plank to more easilymate into the connector.

In the present invention, while each of the thermoplastic laminateplanks can be affixed to the sub-floor or substrate, it is preferredthat the thermoplastic laminate planks be attached only to each otherthrough the groove system such that there is a floating floor system.This promotes fast and easy laying of the floor system.

With the thermoplastic laminate planks of the present invention, thepresent invention achieves many benefits and advantages, such asmoisture resistance, mechanical properties such as impact strength,resistance to indentation and gouges, and beneficial acousticalproperties. Further, the laminate plank system of the present inventioncan be used in any environment, dry or wet, indoor or outdoor since itis not susceptible to moisture damage or distortion. In an embodiment ofthe present invention, the planks are less sensitive to the combinedeffects of temperature and humidity than is the standard laminateproduct. As a result, the need for T-moldings to act as expansion andcontraction areas of the floor can generally be eliminated. TheseT-moldings are not only unsightly, but can act as tripping hazards. Bythe elimination of T-moldings/expansion joints in the walkway, thepresent invention allows the use of the floor in commercialapplications. In an embodiment, the present invention expanded only onefifth as much as a standard laminate product under identical conditions.These conditions take the product from ambient room conditions toconditions of 100% relative humidity and 90° F. Standard expansionjoints for laminate are typically placed every 30 feet. Thus, a hallwayof 150 feet would be feasible without an expansion joint according tothe present invention.

A second study shows that by post conditioning the planks, such as at240° F. for varying times of from 20 to 40 seconds, the planks may berendered even more stable. This treatment is referred to as thermalbalancing. Results are described in the table below.

Growth in Growth in Description of Flooring Width** Length** Plank #1*0.03% 0.03% Plank #2* 0.03 0.03 Plank #3* 0.04 0.03 Laminate Plank(Comparison) 0.10 0.20 (Commercial product) *present invention**Conditions start at ambient room conditions. Product expands duringchange to 90° F. and 100% RH.

Also, in the preferred embodiment of the present invention, theinstallation method used as a result of the unique designs of thethermoplastic laminate planks of the present invention, preferablyeliminates the glue needed for tongue and groove connections.

In the preferred embodiment of the present invention, the installationmethod utilizes the unique design of the product to eliminate the needfor glue used in tongue and groove connections.

Furthermore, the installer has options for installing the thermoplasticlaminate plank product. In one method, a floating floor installationmethod can be utilized. In this method, no adhesive is applied to bondthe product to the subfloor surface. The benefits of this method havebeen described earlier.

In a second method, a full-spread adhesive is applied between theunderside of the product and the sub-floor surface. This provides theadvantages of added dimensional stabilization and sound deadening. Bothof these properties would be beneficial in commercial applications.

In addition, the excellent moisture resistance and sound deadeningqualities of this product can eliminate the need for underpadding,though use of underpadding is an option.

A further embodiment of the present invention relates to a thermoplasticplank which comprises the same plank described above but, in lieu of alaminate on top of the plank, a design is printed directly on the topsurface of the plank using any number of printing techniques such asgravure printing, transfer printing, digital printing, flexo printing,and the like. Or, a printed thermoplastic film (e.g., PVC) or a woodveneer and the like can be laminated to a thermoplastic plank. Aprotective coating can then be placed on top of the printed design. Anytype of protective coating or wear layer can be used such as apolyurethane type coating with or without wear resistant particles inthe coating. Thus, a thermoplastic plank would comprise a corecomprising at least one thermoplastic material where the core has a topsurface and bottom surface as well as opposing sides and a printeddesign directly on the top surface of the plank and optionally at leastone protective coating on top of the printed design. The top surface ofthe plank as described earlier, can have a textured surface as describedabove.

This type of thermoplastic plank can be made by extruding at least onethermoplastic material into the shape of the core and then printing adesign directly on the top surface of the plank and then optionallyapplying at least one protective coating on top of the printed designand curing the protective coating. The protective coating can be appliedby conventional techniques, such as curtain coater, direct roll coater,differential roll coater or air knife coater or spray apparatus.

In another embodiment of the present invention, a thermoplastic plankfor surface coverings, such as flooring, has a thermoplastic core asdescribed above in the other embodiments and a extruded layer on the topsurface of the core wherein this extruded layer comprises at least onethermoplastic material with one or more pigmented compounds. Thisextruded layer on top of the extruded core can simulate various designssuch as wood grain and the like.

The thermoplastic plank in this embodiment can be made by co-extrusiontechniques which involve extruding at least one thermoplastic materialinto the shape of a core and extruding either simultaneously orsubsequently a layer containing at least one thermoplastic material withone or more pigmented compounds on top of the extruded core.

Another embodiment involves a thermoplastic plank having the same designas described above with a printed polymeric film, such as a PVC filmplaced on the top surface of the extruded core. The printed polymericfilm can be a polymeric film having a printed design on the film whereinthe film would preferably be from about 10 to about 20 mil thick. One ormore wear layers or protective coatings can be placed on top of theprinted polymeric film. The polymeric film can be placed on top of theextruded core by typical lamination techniques such as heating theprinted film, then pressing the film to the extruded core to bond themtogether, or using glue to bond them together.

In more detail and with reference to the Figures, the Figures showvarious aspects of several embodiments of the present invention. In eachof FIGS. 1–6, the length measurements shown are in units of inches andangle values are shown in degrees. For each measurement set forth indecimal form, the tolerance is +/−0.005 inch per measurement. For eachmeasurement set forth in fraction form, the tolerance is +/− 1/16 inchper measurement. For each angular measurement, the tolerances is+/−0.5°.

With reference to FIG. 1, FIG. 1 represents a schematic diagram of anend view of one embodiment of the thermoplastic plank. FIG. 1 is aperspective view looking at the front edge of the thermoplastic plankwherein the groove (76) would run along each longitudinal edge of theplank. The spline or tongue (64) is inserted along the length of eachgroove (76). (72) points to the edges of the spline having the groovewhereas (68) points to the lower or bottom surface of the plank and (70)points to the top surface or the surface that typically but optionallyreceives the print layer and the like. (62) refers to the feet or stripsof post-extruded material which extend along the bottom surface of thecore from the front edge to the back edge. As can be seen in FIG. 1,typically these post extruded lines of thermoplastic material act as asupport mechanism and typically run parallel in the same paralleldirection as the cavities (60). Preferably, and as shown in theembodiments in FIG. 1, the edge side of the plank which has a groove istypically tapered or beveled as shown at (78). The cavities (60) areshown in FIG. 1 as having rectangular cross-sections. The cavitiesextend longitudinally along the length of the plank, preferably alongthe entire length of the plank from one end to an opposing end.

In the embodiment of FIG. 1, the overall width (from left to right inthe view shown) of the plank is 7.000 inches (178 mm) not including thesplines or tongues 64 shown connected at each end of the plank. Thelength of the plank (not shown) is 72 inches (1829 mm). The width ofeach cavity (shown from left to right) is 0.335 inch (8.51 mm). Thevertical dimension of the upper and lower wall thicknesses above andbelow each cavity is 0.070 inch (1.78 mm) each. The height (in avertical dimension) of each cavity is 0.215 inch (5.46 mm). The width(from left to right) of the vertically disposed side walls betweenadjacent cavities is 0.060 inch (1.52 mm) with the exception of theoutermost side walls adjacent the grooves 76, which each have a width of0.116 inch (2.95 mm).

Referring to FIG. 2, FIG. 2 is a representation of one type of spline ortongue (64) that can be used in one embodiment of the present invention.As can be seen in FIG. 2, the preferably soft material (82) such as PVCis located on the top and bottom surface of the spline or tongue inorder to ensure a tighter fit with the groove of the thermoplasticplank.

The spline design preferably has a thickness of from about 3 mils (0.13mm) to 5 mils (0.26 mm) thicker than the groove of the plank. If thespline is too thick, it can open the groove and cause edge peaking. Ifthe spline is too thin, it does not effectively engage with the teeth inthe groove. The edges of the spline or tongue (64) are tapered orbeveled as shown at (80) in order to ensure that the tongue can beinserted into the groove.

In the embodiment shown in FIG. 2, the overall width of the spline ortongue 64 (from left to right) is 0.500 inch (12.7 mm) and the overallheight is 0.180 inch (4.57 mm).

The thickness of the soft material 82 shown on the top and bottom of thespline or tongue is 0.023 inch (0.58 mm). For each of the top and bottomsurfaces of the spline, the respective surface is made up of 0.064square inch (1.63 mm) of a rigid polyvinylchloride (PVC) material and0.019 square inch of a soft polyvinylchloride material. The angledcorners of the spline or tongue 64 are each angled about 30° withrespect of the flat top and bottom respective adjacent surface of thespline or tongue 64.

FIG. 3 makes reference to a spline (64) which has teeth (90) on itssurfaces which engage the grooves (76) of the thermoplastic planks.Further, as can be seen in FIG. 3, in a preferred embodiment, the topsurfaces of the plank form a V shape valley (88) and the top edges ofthe adjacent planks touch each other whereas the bottom edge portions ofeach respective plank are cut in order to have a slightly shorter lengthand thus form a gap (86) which ensures that the top ends (88) touch eachother and do not leave any gaps on the walking surface of the planks.Reference numeral (84) shows a top layer, such as a print layer, acomposite print layer, or the like.

In the embodiment shown in FIG. 3, the width dimension of the gap 86(from left to right) is 0.030 inch (0.76 mm). The thickness of the toplayer 84 shown in FIG. 3 is 0.015 inch (0.38 mm). The surface area,viewed from the bottom, of the feet or strips 62 of post-extrudedmaterial is 0.0048 square inch (0.122 mm) each and they are made of asoft polyvinyl chloride material. The total surface area, covered byfeet or strips 62, of the bottom of either plank shown connected in FIG.3 is 0.0624 square inch (1.60 mm). The two connected planks shown inFIG. 3, each have dimensions of from about 7.0 inches in width and about72 inches in length, and each is provided with 13 feet or strips 62.

Referring to FIG. 4, FIG. 4 is a depiction of a groove (76) which hasreceiving teeth (92) for a spline or tongue of the design shown at (90)in FIG. 3. FIG. 4 further shows the post extruded lines (62) on thebottom surface of the extruded plank as well as the various angles andcuts of the cavity (60). Further, the beveled or tapered edge (78) isshown in FIG. 4.

In the embodiment shown in FIG. 4, the foot 62 has a width of 0.075inch, a height of 0.075 inch, and is housed in a corresponding groove orhole that extends 0.050 inch into the bottom surface of the flooringplank. As such, 0.025 inch of the foot extends past the bottom surfaceof the plank. The cavity 60 shown in FIG. 4 has an upper corner definedby a radius of curvature of 0.025 inch and a bottom corner including a45° angle wall that intersects with the side wall and the bottom wall ofthe cavity in radii of curvature of 0.025 inch each. The beveled ortapered edge 78 shown in FIG. 4 is angled in an amount of 17° relativeto the flat top surface of the plank. The beveled or tapered bottom edgeopposite edge 78 is angled in an amount of 30° relative to the flatbottom surface of the plank. The receiving teeth 92 are each 0.040 inchwide (from left to right) and each has a flat top surface at its pointthat has a width of 0.008 inch. The gap between opposing top and bottomteeth is 0.150 inch. The depth of the groove 76, from the edge of theplank to the deepest part of groove 76 (from left to right) is 0.270inch and the depth from the left edge of the plank to and including thelast tooth within the groove is 0.201 inch. The beveled or tapered edge76 intersects with the flat top surface of the plank 0.125 inch from theedge of the plank.

FIGS. 5 and 6 represent various different widths of the plank butgenerally show the same features as shown in FIG. 1 and the referencenumerals in FIGS. 5 and 6 represent the same features as thecorresponding numerals represented in FIG. 1.

The dimensions of the cavities and wall thicknesses of the embodimentshown in FIG. 5 are substantially identical to the dimensions shown inFIG. 1 with the exception that the overall width of the plank shown inFIG. 5 is 3.000 inches as opposed to 7.000 inches for the width of theplank shown in FIG. 1. In addition, the two vertical side walls adjacenteach respective gap 76, herein referred to as the two outermost sidewalls, are 0.075 inch in width as opposed to 0.116 inch in width for thecorresponding outermost side walls of the embodiment shown in FIG. 1.The overall height of the plank shown in FIG. 5, from the flat topsurface to the flat bottom surface (excluding the feet or strips 62) is0.355 inch for the embodiment shown in FIG. 5.

For the embodiment shown in FIG. 6, the dimensions are substantiallyidentical to those dimensions shown in the embodiment of FIG. 5, withthe exception that the plank shown in FIG. 6 has an overall width of5.000 inches and each cavity has a width of 0.303 inch.

FIG. 7 depicts yet another embodiment of the thermoplastic plankaccording to the present invention. FIG. 7 is an end view of anembodiment wherein the extruded thermoplastic plank has a substantiallyplanar top surface (92), and a bottom surface (94) having a plurality ofchannels formed therein, wherein each channel (96) extendslongitudinally from one end of the plank to the other end of the plank.The channels can be U-shaped, u-shaped, or have any other suitable crosssectional shape. The channels (96), when the planks are in place on afloor, can house any of a variety of electrical or signal-carryingwires, cables, cords, or conduits. The plank is significantly lighterthan a similar plank having the same dimensions but without having thechannels formed therein. A flooring system made of such planks has asofter feel and a lighter weight than an otherwise similar but solidplank. As shown in FIG. 7, a centering pin (98) and a pin receiving hole(100) are each provided on both ends of the plank so that adjacentplanks can be aligned with each other in an end-to-end configuration.

The thermoplastic planks of the present invention can be used in avariety of applications including, but not limited to, wall panels,ceiling panels, flooring surfaces, decks, patios, furniture surfaces,shelving, and other surface coverings or parts thereof.

The present invention will be further clarified by the followingexamples, which are intended to be purely exemplary of the presentinvention.

EXAMPLES Example 1

Compound:

In one case a PVC compound containing impact modifier, filler,stabilizer and processing aids in the amounts below was extruded througha profile die giving a hollow cross section as shown in FIGS. 1, 5,and/or 6.

Ingredient Amount (phr) PVC Homopolymer 100 Thermal Stabilizer 0.8–1.5Processing Aid 0.5–1.0 Impact Modifier 3.0–4.0 Lubricant internal0.6–1.0 external 1.1–1.5 Filler 20–35 TiO₂ 1.5–3.0 Barrel 1 Barrel 2Barrel 3 Barrel 4 Barrel 5 Barrel Temperatures, deg. 345–360 345–360320–340 315–330 90–110 F. Oil Temperature deg. F. (through screw)285–300 Die 1 Die 2 Die 3 Die 4 Die 5 Die Temperatures, deg F. 345–360360–370 360–370 380–390 370–380 Percent Load   63–75% Main RPM  950–1100 Output   356–550 pounds/hr (163–250 kg/hr) Back Pressure 18.1–19.0 metric tons Melt Pressure 4,075–4500 psi Melt Temperature,deg. F.   385–390 Color Feeder  0.35–0.70 pounds/hr (setting of 5 for0.35, setting of 10 for 0.70) Line Speed  8.5–8.75 feet/min CalibrationUnit: Vacuum 1    16–20 in Hg Vacuum 2    17–20 in Hg Vacuum 3 12.5–15.0in Hg Vacuum 4 off Puller Force 3560–4000 pounds Water Temperature, ° F.61 Pressure at Cooling and Sizing, psi #1 40 mbar #2 40 mbar ClampingPressure at conveyor Front 40–45 psi Back 28–35 psi Counterbalance 33–40psi Specific Applications Wrapping Conditions: Layout ofline/Conditions:

A machine was used to form the HPL (High Pressure Laminate top layer)onto the PVC Plank Base. The machine was called a “wrapping machine” andis composed primarily of two main parts 1) a forming action component toshape the HPL to the contour of the base, and 2) a clamping actioncomponent to retain the HPL shape onto the base as the adhesive coolsand strengthens.

In more detail:

-   -   1. PVC Planks were placed onto the line to be conveyed through        by rubber covered roller wheels. Speed of conveyance was 35–50        feet per minute in this particular application. In other        applications, speeds may range as high as 120 fpm.    -   2. PVC Planks underwent surface treatment to raise surface        tension and improve the wetting of adhesive onto the surface.        The surface treatment unit which was from Corotec, 145 Hyde Rd,        Farmington, Conn., provided plasma jet treatment. The surface        tension was raised from 34 to 45+ dynes/cm.    -   3. HPL (laminate) top layer, dispensed in a continuous roll, was        treated with a polyurethane hot melt adhesive, Reichold 2U145,        available from Reichold Chemicals, 2400 Ellis Rd, Durham, N.C.        The adhesive was heated to 237 degrees F. and rolled onto the        back of the HPL layer with a knurled roll.    -   4. The HPL was then mated to the PVC Plank, and IR heat was        directed onto the face of the HPL. Temperature on the face of        the PVC Plank was raised to 300° F.–330° F., which softens the        HPL enough to allow shaping.    -   5. The HPL was shaped using rubber rollers onto the face of the        PVC plank and down the beveled edges of the plank. As such, this        wrapping process shaped the HPL to adhere to the topography of        the plank onto which it is being affixed.    -   6. Water spray quickly lowered the temperature of the HPL/PVC        Plank assembly to below 100° F. (e.g., 94 ° F.). Rubber rollers        continued to hold the HPL onto the PVC surface while the        assembly cooled further. This allowed the adhesive to cool and        strengthen, thereby permanently affixing the HPL top layer to        the PVC Plank lower layer.    -   7. Each individual plank assembly was then separated from the        following planks with a force appropriate to make a sharp        separation.        Post-Treatment:        Mechanical Post-Treatment

The HPL/PVC Plank assembly was then finished with end cutting and edgetrimming procedures to cut the board ends square and trim the laminateoverhang flush to the base plank.

Thermal Post-Treatment

Due to the uneven top-side heating of the HPL/PVC Plank assembly duringshaping, the finished product can develop a “cup” distortion where thetop ends of the plank come closer together. In order for the plank tolie flat, this must be countered with an opposing thermal treatment onthe back side of the HPL/PVC Plank Assembly. Thermal treatment can bedone in line by directly heating (in an upward direction) the bottomsurface of the plank while the plank is undergoing the wrapping process.

For the specific HPL/PVC Plank geometry shown in FIG. 1, it has beenfound that by heating the back surface of the assembly to certaintemperatures for certain times, the shape of the board can becontrolled. In fact, the cupping can be corrected and a flat plankproduced if the board is heated to 240–300 degrees F. for 20–45 seconds.

If the board is allowed to reside at higher temperatures for longertimes, a “doming” can actually be induced into the board. So totalcontrol of the ultimate shape of the board can be achieved byappropriate selection of conditions.

The thermoplastic plank of the present invention was tested forproperties and compared to commercially available Mannington laminateand wood flooring products.

The can drop test involved dropping a 2 lb can from 40 inches high,wherein 100% means a puncture of the product and 0% means no chip off.

Extrusion Plank Testing

Mannington Product Extrusion Plank Test Designation Laminate Wood PlankOnly With Overlay Taber Abrasion, cycles to IP 9880 125 5 mils @ 5005590 Can Drop, mils indent* MD, no feet 30, 100% cat 50, 100% cat 5, 16%cat  5, 0% cat AMD, no feet 30, 100% cat 31, 100% cat  1, 0% cat  1, 0%cat MD, with feet — — 7, 28% cat 5, 60% cat AMD, with feet  1, 0% cat 0, 0% cat Pneumatic Indent, mils indent No feet 0 3.6 0.2 0 With feet —— 0.2 0.2 Two hour stain KC-261 Asphalt (Sealer) 0.5 0 3 0 Shoe Polish 01 0 0 Oil Brown 0.5 0 0 0 Mustard 0 0 0 0 Chemlawn 0 0 0 0 Blue Sharpie0.5 0.5 0.5 0 Iodine 0 3 0 0 Total Stain 1.5 4.5 3.5 0 Static Load, milsindent No feet 0 1 0 0 With feet — — 0 0 Sliding Gouge MD, no feet 250psi pass pass pass pass 300 psi pass fail pass pass 350 psi pass failpass pass AMD, no feet 250 psi pass pass pass pass 300 psi pass failpass pass 350 psi pass fail pass pass MD, with feet 250 psi — — passpass 300 psi — — pass pass 350 psi — — pass pass AMD, with feet 250 psi— — pass pass 300 psi — — pass pass 350 psi — — pass pass Two hourboiling water fail fail pass pass Large ball impact, inches to failureNo Feet 14 10 32, no failure 32, no failure With Feet 32, with pad — 32,no failure 32, no failure This row indicated “cat” as catastrophicfailure meaning puncture through.

Example 2

A series of thermoplastic planks similar in design to the planks formedin Example 1 were connected together to create a flooring system. Thespline system as set forth in FIG. 3 was used. In addition, a comparisonwas made with using no bonding agent and a flooring system using abonding agent. The bonding agent, tetrahydrofuran (THF) was applied toall sides of the plank including the spline and grooves. When no THF wasapplied to the spline area, the bonding strength was an average of 1.73pounds using the Instron test with the following parameters: 50 poundsfull scale for the chart paper, 0.5 in/minute jaw speed, 3 inch jawdistance, 1×5 sample, 156 mil spline thickness. When the same type ofextrusion plank had THF applied to the spline area, after 4 hourscuring, the bonding strength of the spline area was an average of 18.1pounds and after 24 hours curing, the bonding strength of the splinearea was 39.1 pounds. The ends of the extrusion plank were tested forbonding strength wherein the ends have no spline attachment and simplybutted against each other.

There was no bonding strength when no THF was present since there isnothing holding the edges of each plank together. When THF was appliedto the edges after 4 hours cure, the bonding strength was over 100pounds using a 100 pound scale, and after a 24 hour cure, the bondingstrength was over 100 pounds using a 100 pound scale. When the test wasrepeated with a 152 mil spline with THF, using the INSTRON test, after24 hour cure, the bonding strength was an average of 45.37 pounds.

A rolling secretary test using 165 pounds was then used. In this test, a20 by 30 inch panel was used wherein a half of the panel was THF bondedover 24 hours and the other half of the panel had only splines holdingthe panels together. This panel was then laid on a carpet which causedmovement up and down on the panel. The product with the 156 mils splineseparated after 20 cycles and the other half of the product, which wassealed with THF, did not separate after 150 cycles. This was impressiveconsidering the panel was not glued down to any surface.

A second panel was then made and placed on a sterling board with feltshim (0.26 inch) and placed in different places on the PVC board. Thiswas done to cause unevenness in the subfloor. Upon doing the rollingsecretary test again, the planks did not separate with the THF present.

Both products were then tested by placing them on towels and water wasplaced on the end cuts and the spline area. After 10 minutes, the waterwas wiped and the THF end cut area had very little penetration of waterwherein the non-sealed area did show signs of leakage.

In the 75 pound slider test which was developed as a spline strengthtest, a 12 inch long spline was inserted into the tongue of a 12 inchplank and then a second plank was connected to the other side of thespline in order to connect two planks together. A hole was then drilledin the middle of one of the planks. With the two planks connectedtogether, 75 pounds was placed on the plank without the hole and a 50pound fish scale was hooked to the plank with the drilled hole andslowly pulled until the connected planks separated. With a 150 mil thickspline and a vertical gap thickness of PVC plank of approximately 154mil on average, the product pulled apart from the spline after a staticfriction reading of about 25 pounds initial pull wherein the pull wasdone on a Lauan substrate. Using a spline that was 156 mil thick, thespline went in with some tapping and the test was done both on a Lauanand Sterling board substrate which gave different readings on the fishscale. With respect to the Sterling board substrate (static friction) of40 pounds and (dynamic friction) of 35 pounds, the product did not pullapart. With respect to the Lauan (static friction) of 25 pounds and(dynamic friction) of 20 pounds, the product did not pull apart. A 159mil spline was then used which was hard to install due to the thicknessof the receiving tongue, in this test, Sterling (static friction) of 35pounds and (dynamic friction) pulled apart but took some effort and theproducts did not move at all. With respect to the Lauan (staticfriction) of 35 pounds and (dynamic friction) of 30 pounds, the productslid but no separation.

In view of the above testing, these examples show that the addition ofTHF as a bonding agent provides significant strength advantages to theoverall surface covering systems and also prevents water penetration tothe subfloor especially at the edges where there is no spline systemused.

Other embodiments of the present invention will be apparent to thoseskilled in the art from consideration of the specification and practiceof the present invention disclosed herein. It is intended that thespecification and examples be considered as exemplary only, with thetrue scope and spirit of the present invention being indicated by thefollowing claims.

1. A thermoplastic laminate plank comprising: a core comprising at leastone thermoplastic material and wood filler, wherein said core has a topsurface and a bottom surface, and opposing sides; a print layer affixedto said top surface of said core, wherein said print layer has a topsurface and a bottom surface; and a protective layer affixed to said topsurface of said print layer, wherein said thermoplastic laminate plankis domed and with the proviso that no backing layer is located adjacentthe bottom surface of said core.
 2. The plank of claim 1, wherein saidwood filler is wood flour.
 3. The plank of claim 1, wherein said woodfiller is present in an amount of from 10 to about 35 parts by weightbased on 100 parts by weight of the thermoplastic material.
 4. The plankof claim 3, wherein said wood filler is wood flour.
 5. The plank ofclaim 1, further comprising an underlay layer located and affixedbetween said bottom surface of said print layer and said top surface ofsaid core.
 6. The plank of claim 1, wherein said core further comprisesat least one plasticizer.
 7. The plank of claim 6, wherein said at leastone plasticizer is present in an amount of less than about 20% by weightof said core.
 8. The plank of claim 1, wherein said at least onethermoplastic material is polyvinyl chloride.
 9. The plank of claim 1,wherein said core has a thickness of from about 5 mm to about 20 mm, awidth of from about 2 cm to about 30 cm, and a length of from about 30cm to about 130 cm.
 10. The plank of claim 1, wherein said core has aseries of paralleled cavities.
 11. The plank of claim 1, wherein saidplank has at least one groove located on a side of said core.
 12. Theplank of claim 1, wherein said plank has at least one tongue and onegroove located on the plank.
 13. The plank of claim 1, wherein two sidesof said core are tapered or have beveled edges, wherein said sides areopposite to each other.
 14. The plank of claim 1, wherein said printlayer comprises an aminoplast resin impregnated printed paper.
 15. Theplank of claim 14, further comprising a printed design.
 16. The plank ofclaim 1, wherein said overlay comprises an aminoplast resin impregnatedoverlay paper and aluminum oxide imbedded on the top surface of saidpaper.
 17. The thermoplastic laminate of claim 1, wherein saidthermoplastic material comprises at least one thermoplastic resin, atleast one processing aid, at least one impact modifier, at least onelubricant, and at least one stabilizer.
 18. The thermoplastic laminateof claim 17, wherein said thermoplastic material further comprises atleast one pigment.
 19. A surface covering comprising a plurality ofthermoplastic laminate planks of claim 1, joined together.
 20. Thesurface covering of claim 19, wherein said surface covering is a floorcovering that is a floating floor installation.
 21. A floor coveringcomprising a plurality of thermoplastic laminate planks, wherein saidfloor covering is a floating surface and wherein said thermoplasticlaminate plank comprises: a core comprising at least one thermoplasticmaterial and wood filler, wherein each core has a top surface and abottom surface, and opposing side, and wherein said bottom surface isthermally treated by direct heating of the bottom surface; a print layeraffixed to said top surface of said core, wherein said print layer has atop surface and a bottom surface, and wherein said print layer includesan aminoplast resin impregnated printed paper, and a protective layeraffixed to said top surface of said print layer, with the proviso thatno backing is located adjacent the bottom surface of said core.
 22. Thefloor covering of claim 21, wherein at least a portion of saidthermoplastic laminate planks are joined together by splines.
 23. Thefloor covering of claim 21, wherein at least a portion of saidthermoplastic laminate planks are joined together by a bonding agent.24. The floor covering of claim 23, wherein said bonding agent istetrahydrofuran, methylene chloride, a ketone, or combinations thereof.25. A thermoplastic laminate plank comprising: a core comprising atleast one thermoplastic material and wood filler, wherein said core hasa top surface and a bottom surface, and opposing sides; a print layeraffixed to said top surface of said core, wherein said print layer has atop surface and a bottom surface, and wherein said print layer includesan aminoplast resin impregnated printed paper; and a protective layeraffixed to said top surface of said print layer, with the proviso thatno backing layer is located adjacent the bottom surface of said core,wherein at least said bottom surface of the core is thermally treated bydirect heating of the bottom surface.
 26. The plank of claim 1, whereinsaid core has a surface tension of 34 dynes/cm or higher.
 27. The plankof claim 1, wherein said core has a surface tension of 45 dynes/cm orhigher.
 28. The plank of claim 1, wherein said core has moistureresistance such that said core does not expand more than 0.04% in widthor in length when subjected to conditions that subject the core fromambient conditions to 100% relative humidity and 90° F.
 29. Athermoplastic laminate plank comprising: a core comprising at least onethermoplastic material and wood filler, wherein said core has a topsurface and a bottom surface, and opposing sides; a print layer affixedto said top surface of said core, wherein said print layer has a topsurface and a bottom surface; a protective layer affixed to said topsurface of said print layer; a surface tension of 34 dynes/cm or higher;and a moisture resistance such that said core does not expand more than0.04% in width or in length when subjected to conditions that subjectthe core from ambient conditions to 100% relative humidity and 90° F.